What part of the backbone attaches to the base pairs?

Attached to each sugar is one of four bases--adenine (A), cytosine (C), guanine (G), or thymine (T). The two strands are held together by bonds between the bases, with adenine forming a base pair with thymine, and cytosine forming a base pair with guanine.

Explanation:

located offshore, in the arctic and pacific oceans

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.